Roller screw and method of circulating rollers in roller screw

Abstract

There is provided a roller screw in which a twisted amount of an unloaded return path is reduced. The roller screw has a screw shafthaving a spiral roller-rolling surfaceon an outer peripheral surface thereof; a nuthaving a spiral loaded roller-rolling surfaceon an inner peripheral surface thereof, the spiral loaded roller-rolling surface being opposed to the roller-rolling surfaceof the screw shaft; a circulation memberarranged in the nutand formed to have an unloaded return pathconnecting one end and the other end of the loaded roller-rolling surface, whose turn number is less than one, of the nut; and a plurality of rollersarranged in a one-turn roller circulation path composed by a loaded roller-rolling pathand the unloaded return path. The circulation memberguides the rollers which have moved and arrived at the one end of the loaded roller-rolling pathhaving less than one turn, to the unloaded return path, and then returns the rollers to the other end of the loaded roller-rolling pathhaving less than one turn. The number of turns of the loaded roller-rolling pathis set to be less than one turn, whereby the rollerswhich have arrived at one end of the loaded roller-rolling pathcan be transferred to the other end of the loaded roller-rolling pathwithout changing their attitudes.